- Widgets from the @aria library can be customized to a certain extent using the skinning system. Unfortunately, documentation has not been migrated here yet so I'll MP the topspot links. Note that you will be able to customize the aspect of the widgets, not the markup they generate.

- Widgets from the @html library generate only standard html elements which can be styled using CSS.

- You can also create your own set of widgets, in which case you have obviously total control over the generated markup and potential skin properties you'd like to publish.